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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

28070 results found.

  1. EP-WXT01709259790: Xinglong optical upper limit
  2. GRB 260410A: Fermi-LAT detection
  3. GRB 260410A: Fermi GBM Final Real-time Localization
  4. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  5. EP260321a: Chandra X-ray Non-detection
  6. GRB 260409A: Fermi GBM Final Real-time Localization
  7. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  8. The EP-WXT trigger 01709259773 is likely a flaring star
  9. GRB 260407A: GECAM-A detection
  10. GRB 260407A: Insight-HXMT/HE detection
  11. EP260409a: SVOM/VT optical upper limits
  12. EP260409a: COLIBRÍ optical upper limits
  13. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  14. EP260409a: Global MASTER-Net observations report
  15. EP260321a: VLA radio detection
  16. GRB 260404A: Fermi GBM Final Localization
  17. GRB 260407A: Glowbug gamma-ray detection
  18. GRB 260402A: SVOM/ECLAIRs refined analysis
  19. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  20. GRB 260310A / AT2026fgk: X-ray rebrightening
  21. EP260402a / GRB 260402A: Mephisto optical upper limits
  22. EP-WXT01709259586: Xinglong optical upper limit
  23. EP260403a: Mephisto optical upper limits
  24. EP260402a/GRB 260402A: Xinglong optical upper limit
  25. EP260321a: Upper limits from VLA radio observations
  26. GRID detection of GRB 260401A
  27. EP260321a: uGMRT observations
  28. GRB 260407A: Fermi GBM Final Real-time Localization
  29. EP260405a: GMOS-N optical upper limits
  30. EP260405a: SVOM/VT optical upper limits
  31. EP260405a: Global MASTER-Net observations report
  32. EP260405a: Einstein Probe detection of a fast X-ray transient
  33. The EP-WXT trigger 01709259621 is likely a flaring star
  34. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  35. The EP-WXT trigger 01709259615 is likely a flaring star
  36. Fermi trigger No 797039833: Global MASTER-Net observations report
  37. GRB 260403A: GECAM-B observation of a long burst
  38. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  39. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  40. The EP-WXT trigger 01709259586 is likely a flaring star
  41. GRB 260330B: SVOM/VT further optical observation
  42. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  43. GRB 260330B: SVOM/ECLAIRs refined analysis
  44. EP260403a: LCO optical observations of the counterpart
  45. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  46. EP260403a: LCO optical counterpart detection
  47. EP260403a: COLIBRÍ optical counterpart candidate
  48. GRB 260330B: SVOM/VT optical candidate
  49. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  50. GRB 260403A: AstroSat CZTI detection
  51. GRB 260402B: GECAM-B observation
  52. EP260324A / AT 2026hir: COLIBRÍ optical observations
  53. GRB 260403A: Fermi GBM Final Real-time Localization
  54. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  55. GRB 260402B: Fermi GBM Final Real-time Localization
  56. GRB 260402A: WINTER J-band upper limit
  57. GRB260402A: GROWTH-India Telescope optical upper limit
  58. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  59. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  60. GRB 260401A: SVOM/GRM observation
  61. GRB 260401A: GECAM-B observation
  62. GRB 260402A: MASTER optical observations
  63. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  64. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  65. GRB 260402A: SVOM detection of a burst
  66. Fermi GRB 260401A: Global MASTER-Net observations report
  67. GRB 260401A: Fermi GBM Observation
  68. GRB 260401A: NuSTAR detection of prompt emission
  69. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  70. GRB 260401A: MAXI/GSC detection
  71. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  72. GRB 260401A: Fermi GBM Final Real-time Localization
  73. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  74. EP260321a :Xinglong optical observations
  75. EP260327a: Xinglong optical upper limit
  76. EP260329b: GOTO detection of optical counterpart
  77. GRB 260330B: SVOM/VT optical upper limits
  78. Konus-Wind detection of GRB 260316B
  79. GRB 260321A: SVOM/ECLAIRs refined analysis
  80. EP260329b: J-band upper limits with WINTER
  81. EP260329a: J-band upper limit with WINTER
  82. GRB 260330A: Glowbug gamma-ray detection
  83. GRB 260310A: VLA Multi-frequency Radio Observations
  84. Fermi GBM Sub-Threshold Detection of GRB 260330B
  85. GRB 260330B: LCO optical upper limits
  86. GRB 260330B: SVOM detection of a burst
  87. EP260329a: COLIBRÍ optical upper limit
  88. EP260329a: EP-FXT follow up observation
  89. EP260329a: NOT optical counterpart candidate
  90. GRB 260330A: Fermi GBM Final Real-time Localization
  91. EP260329b: Global MASTER-Net observations report
  92. Fermi trigger No 796485221: Global MASTER-Net observations report
  93. EP 260329b: COLIBRÍ optical observations
  94. EP260329b: LCO optical observations of the counterpart
  95. GRB 260326A: Insight-HXMT/HE detection
  96. EP-WXT trigger 01709259209: TRT optical counterpart detection
  97. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  98. GRID detection of GRB 260326A
  99. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  100. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations

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